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Here is your complete clinical posting guide on Anatomy of the Female Pelvis - structured for MBBS clinical year.

Anatomy of the Female Pelvis - OB/GY Clinical Posting

1. Bony Pelvis

The pelvis is divided into the true pelvis (below the pelvic brim) and false pelvis (above it). The dividing line - the linea terminalis (pelvic brim) - runs from the sacral promontory posteriorly to the superior edge of the pubic symphysis anteriorly.

Bones

The true pelvis is formed by 4 bones:

2 innominate (hip) bones - each made up of ilium, ischium, and pubis
Sacrum
Coccyx

Female vs. Male Pelvis - Key Differences

Feature	Female	Male
Inlet shape	Oval/round (gynecoid)	Heart-shaped
Inlet width	Wider	Narrower
Subpubic angle	Obtuse (>90°)	Acute (<90°)
Sacrum	Shorter, wider, less pronounced promontory	Longer, narrower
Pelvic walls	Wider apart	Closer

The female inlet is oval and wider, facilitating childbirth, but this contributes to relative pelvic floor weakness. - Campbell-Walsh-Wein Urology, p. 3215

2. Pelvic Inlet & Outlet Diameters (Obstetric Importance)

These are high-yield for your OB/GY posting:

Diameter	Measurement	Clinical Note
Diagonal conjugate	12.5-13 cm	Measured clinically per vaginum (sacral promontory to lower border of pubic symphysis)
True/obstetric conjugate	~11 cm	Diagonal conjugate minus 1.5-2 cm; smallest AP diameter of inlet
Transverse diameter of inlet	13 cm	Greatest distance between lineae terminales
Interspinous diameter	11 cm	Distance between ischial spines; narrowest diameter of the outlet
Oblique diameter	12 cm	Sacroiliac joint to opposite iliopectineal eminence
AP diameter of outlet	9 (+2) cm	Lower border of symphysis to tip of coccyx

General Anatomy and Musculoskeletal System (THIEME Atlas), p. 162

The ischial spine is a crucial clinical landmark - it is used for pudendal nerve block and as the reference point for pelvic organ prolapse staging (station 0 = level of ischial spines).

3. Surface Anatomy & Clinical Landmarks

In the anatomical position: the anterior superior iliac spine (ASIS) and the anterior superior edge of the pubic symphysis lie in the same vertical plane. The pelvic inlet faces anterosuperiorly.

Lateral view showing pelvic landmarks and orientation of pelvic inlet, urogenital triangle, and anal triangle

Lateral view - female (A) and male (B) - showing orientation of pelvic inlet and perineal triangles. Gray's Anatomy for Students

Palpable landmarks (use in physical exam):

Iliac crest - from ASIS to posterior superior iliac spine (PSIS)
Pubic symphysis - palpable in midline deep to mons pubis in women
Ischial tuberosities - lateral corners of the diamond-shaped perineum (palpable at the gluteal fold)
Coccyx tip - palpable in midline, posteriorly, defines the posterior limit of the perineum
Ischial spine - felt during vaginal examination; landmark for pudendal block and prolapse staging

Perineum

The diamond-shaped perineum is divided by a line between the ischial tuberosities into:

Urogenital triangle (anterior) - almost horizontal, faces inferiorly
Anal triangle (posterior) - more vertical, faces posteriorly

4. Pelvic Floor

Pelvic floor muscles - levator ani components, coccygeus, perineal membrane, and deep perineal pouch

Pelvic floor anatomy. Gray's Anatomy for Students

The pelvic floor is formed by:

Pelvic diaphragm (levator ani + coccygeus) - the major component
Perineal membrane (anteriorly)
Muscles of the deep perineal pouch (anteriorly)

Levator Ani - THE most important pelvic floor muscle

The levator ani is a broad, thin muscle with 3 named parts:

Part	Origin	Insertion	Key Function
Puborectalis	Posterior aspect of pubic body	Forms U-shaped sling around anorectal junction	Maintains anorectal angle; continence
Pubococcygeus	Posterior pubis + tendinous arch	Anococcygeal raphe + visceral organs	Sling around vagina and urethra (pubovaginal muscle)
Iliococcygeus	Ischial spine + posterior obturator fossa	Coccyx + anococcygeal raphe	Lateral component of pelvic floor

Innervation: Levator ani nerve from S3, S4, S5 (traveling medial to the ischial spine) + branches from pudendal nerve (S2-S4).

Coccygeus: Arises from ischial spine and sacrospinous ligament, inserts on sacrum/coccyx. Completes the posterior pelvic diaphragm.

Levator hiatus: The U-shaped defect anteriorly in the levator ani, through which the urethra, vagina, and rectum pass.

Levator plate: Formed by fusion of levator ani muscles in the midline. Serves as a horizontal shelf for pelvic viscera. Weakening leads to sagging and pelvic organ prolapse.

Sustained resting tone of the pelvic floor supports viscera, resists intra-abdominal pressure, and maintains urinary/fecal continence. - Campbell-Walsh-Wein, p. 3215

5. Pelvic Cavity & Viscera

Pelvic cavity - sagittal section showing peritoneum, levator ani, perineal membrane; and superior view showing uterus, bladder, rectum, iliac vessels

Pelvic cavity and viscera. Gray's Anatomy for Students

Arrangement (anterior to posterior):

Bladder (anterior)
Uterus (middle, between bladder and rectum)
Rectum (posterior)

Peritoneal pouches in women:

Vesicouterine (uterovesical) pouch - between bladder and uterus
Rectouterine pouch (Pouch of Douglas / Cul-de-sac) - between uterus and rectum; the most dependent part of the female peritoneal cavity (fluid collection, endometriosis, ectopic pregnancy)

6. Fascia, Ligaments & Pelvic Spaces

Broad ligament contents and pelvic fascia with cardinal and uterosacral ligaments

Broad ligament and pelvic fascia/ligaments. Campbell-Walsh-Wein Urology

Ligamentous Support of the Uterus

Ligament	Attachment	Contains / Notes
Broad ligament	Lateral uterine walls to pelvic side walls	Double peritoneal fold; contains uterine tubes, round ligament, ovarian ligament, uterine vessels, ureter
Round ligament	Uterine cornua to labia majora (via inguinal canal)	Maintains anteversion of uterus
Cardinal (Mackenrodt's) ligament	Cervix/upper vagina to lateral pelvic walls	Primary support for uterus against downward prolapse
Uterosacral ligament	Posterior cervix to sacrum	Pulls cervix posteriorly; maintains uterine anteflexion
Pubocervical fascia	Surrounds vagina anteriorly	Bladder support

Pelvic Spaces (Surgically Important)

Retropubic (prevesical) space of Retzius - between bladder and pubis
Vesicovaginal space - between bladder and vagina
Rectovaginal space - between rectum and vagina (plane for rectocele repair)
Presacral space - between rectum and sacrum
Paravesical spaces (bilateral)
Pararectal spaces (bilateral)

7. Vasculature

Main arterial supply: Internal iliac artery (hypogastric artery)

Key branches relevant to gynecology:

Uterine artery - crosses OVER the ureter at the base of the broad ligament ("water under the bridge" - ureter is at risk in hysterectomy)
Ovarian artery - arises directly from the aorta (L2 level); runs in the suspensory ligament of the ovary
Vaginal artery - branch of internal iliac
Internal pudendal artery - perineal supply

Venous drainage: Uterine and vaginal venous plexuses drain into the internal iliac vein.

Lymphatic drainage (exam favorite):

Ovaries → para-aortic nodes (L2 level)
Uterine body → iliac nodes and para-aortic nodes
Cervix → external iliac, internal iliac, and obturator nodes
Vulva → superficial inguinal nodes

8. Nerve Supply

Pelvic viscera: Inferior hypogastric (pelvic) plexus (sympathetic T10-L2 + parasympathetic S2-S4)
Pelvic floor muscles: Levator ani nerve (S3-S4-S5)
Perineum: Pudendal nerve (S2-S4) - runs through the pudendal (Alcock's) canal in the lateral wall of the ischiorectal fossa
Obturator nerve (L2-L4): Runs through the obturator canal; at risk in lateral pelvic dissection

9. Clinical Correlations for Your Posting

Anatomical Point	Clinical Significance
Ischial spine	Reference point for fetal station (0 station); pudendal nerve block
Pouch of Douglas	Fluid in this space on USS = haemoperitoneum / PID / ectopic
Uterine artery crossing ureter	"Water under the bridge" - ureteric injury risk in hysterectomy
Levator ani weakness	Pelvic organ prolapse (cystocele, rectocele, uterine prolapse)
Interspinous diameter <10 cm	Contracted pelvis - likely C-section needed
Ovarian lymphatics to para-aortic nodes	Ovarian cancer spreads to para-aortic nodes first
Subpubic angle	Narrow angle = android pelvis = obstructed labour risk

Sources: Gray's Anatomy for Students (5e), Campbell-Walsh-Wein Urology (11e), THIEME Atlas of General Anatomy and Musculoskeletal System.

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